Apparatus and method for data backup

ABSTRACT

A backup control apparatus for periodic data backup, in a virtualized storage system having a point-in-time copy function operable to copy first data into a cascade, comprises a storage targeting component for selecting a target virtual disk for one of a full copy or an incremental copy of the first data; a periodic backup component for triggering a periodic point-in-time copy of the first data to a virtual disk in the cascade; a testing component for testing a status of the full copy, the incremental copy and the periodic point-in-time copy; and a cascade splitting component responsive to the status for splitting the cascade to remove a dependency relationship of at least one of the full copy, the incremental copy and the periodic point-in-time copy on the first data.

PRIORITY CLAIM

This application claims priority to European Patent Application No.09162728.1, filed Jun. 15, 2009, and entitled “Apparatus and Method fora Data Backup.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of backing up of data incomputer systems and more specifically to an apparatus and method forproviding periodic data backups while reducing the risk of datacorruption or loss.

2. Description of Related Art

Users of computer systems have a need to create periodic backups oftheir production data while minimizing the storage used, the impact onthe production I/O and the time that the backups are dependent on theproduction data. Minimizing the storage capacity used and the impact thechosen backup management mechanism has on the production data areobvious requirements for most users. Minimizing the time that backupsare dependent on the production data is a requirement that comes from auser's need to protect backup data from loss of the production data.While the backups are dependent on the production data the system isprotected from corruption of the production data but is not protectedfrom its loss.

SUMMARY OF THE DESCRIBED EMBODIMENTS

Using a space-efficient FlashCopy® (FlashCopy is a Registered Trademarkof IBM Corporation in the United States, other countries, or both) helpsthe user minimize the storage used for backups and that using aFlashCopy solution implemented using a cascade algorithm will minimizethe impact of the backups on the production I/O. At the highest level,FlashCopy is a function where a second image of ‘some data’ is madeavailable. This function is sometimes known in other system contexts asPoint-In-Time copy, or T₀-copy. The second image's contents areinitially identical to that of the first. The second image is madeavailable ‘instantly’. In practical terms this means that the secondimage is made available in much less time than would be required tocreate a true, separate, physical copy, and that this means that it canbe established without unacceptable disruption to a using application'soperation.

Once established, the second copy can be used for a number of purposesincluding performing backups, system trials, and data mining. The firstcopy continues to be used for its original purpose by the original usingapplication. Contrast this with backup without FlashCopy, where theapplication must be shut down, and the backup taken, before theapplication can be restarted again. It is becoming increasinglydifficult to find time windows where an application is sufficiently idleto be shut down. The cost of taking a backup is increasing. There isthus significant and increasing business value in the ability ofFlashCopy to allow backups to be taken without stopping the business.

FlashCopy implementations achieve the illusion of the existence of asecond image by redirecting read I/O addressed to the second image(henceforth Target) to the original image (henceforth Source), unlessthat region (also known as a “grain”) has been subject to a write. Wherea region has been the subject of a write (to either Source or Target),then to maintain the illusion that both Source and Target own their owncopy of the data, a process is invoked which suspends the operation ofthe write command, and without it having taken effect, issues a read ofthe affected region from the Source, applies the read data to the Targetwith a write, then (and only if all steps were successful) releases thesuspended write. Subsequent writes to the same region do not need to besuspended since the Target will already have its own copy of the data.This copy-on-write technique is used in many environments.

Some storage controllers allow a user to configure more than one targetfor a given source, also known as multiple target FlashCopy. This has anumber of applications. For instance, different experiments could be runagainst each of the targets. Or the targets might be taken at differenttimes (e.g. different days in the week), and allow historical access tothe disk, perhaps for the purpose of recovering from some datacorruption, such as might be caused by a virus. One form ofmultiple-target FlashCopy is cascaded FlashCopy.

Cascaded FlashCopy is disclosed in, for example, U.S. Pat. No.7,386,695. In cascade implementations according to the disclosure ofU.S. Pat. No. 7,386,695, such as the multiple target FlashCopy facilityavailable with the IBM SAN Volume Controller (SVC), a write to thesource disk for an area that has not yet been copied will result in thedata being copied to just one of the target disks. For theseimplementations, a read I/O request submitted to a target disk mayrequire FlashCopy to read data from the source disk, the target disk oranother target disk in the cascade depending on which source or targetdisks have previously been written to.

Using these two technologies, it is now possible to construct a solutionthat will protect the production data from corruption up to the requiredrecovery point objective (RPO). However the problem remains of how toprotect the production data from loss up to the required RPO.

Approach 1

The user could take a full incremental copy and take regularspace-efficient Flash Copies between retriggers of the full incrementalcopy. This solution gives the user an RPO for data loss equal to thetime since the full copy was triggered. The RPO for data corruption isequal to the time since the last space-efficient FlashCopy was taken. Ifthe data is lost the production system cannot be recovered from thespace-efficient copies because these copies are dependent on theproduction data. The user must go back to the full copy which must becomplete. If the data is lost before the full copy is complete theproduction data cannot be recovered. This means that users are exposedto data loss whenever they retrigger their full copy.

Approach 2

Another approach is for the user to take a full incremental copy of theproduction data. Then at regular intervals take a space-efficientFlashCopy of the full copy target and then retrigger the fullincremental copy. This means that the user will have more frequentcopies that are independent of the production data once the full copyhas completed. However, while full copy is not complete thespace-efficient copies taken using FlashCopy are dependent on theproduction data, so the act of retriggering causes the user temporarilyto lose some data protection.

Both of the above approaches disadvantageously fail to provide a methodof allowing users to maintain periodic copies of their production datathat are available for recovery from data corruption and data loss whileminimising the storage required and the impact on the production I/O.

The applicant thus believes that it is desirable to alleviate thedisadvantages of the known art by providing an apparatus and methodoperable to provide periodic data backups while reducing the risk ofdata corruption or loss.

The present invention accordingly provides, in a first aspect, a backupcontrol apparatus for periodic data backup in a virtualized storagesystem having a point-in-time copy function operable to copy first datainto a cascade and comprising: a storage targeting component forselecting a target virtual disk for one of a full copy or an incrementalcopy of the first data; a periodic backup component for triggering aperiodic point-in-time copy of the first data to a virtual disk in thecascade; a testing component for testing a status of the full copy, theincremental copy and the periodic point-in-time copy; and a cascadesplitting component responsive to the status for splitting the cascadeto remove a dependency relationship of at least one of the full copy,the incremental copy and the periodic point-in-time copy on the firstdata.

In one embodiment, the cascade splitting component is operable toselectively reattach the at least one of the full copy, the incrementalcopy and the periodic point-in-time copy at a different position in thecascade. In one embodiment, the cascade is controllable by means of arelocatable cascade disk mapping. In one embodiment, the point-in-timecopy function comprises FlashCopy. In one embodiment, the relocatablecascade disk mapping comprises a FlashCopy Fdisk.

In one embodiment, the at least one of the full copy, the incrementalcopy and the periodic point-in-time copy comprises a space-efficientcopy.

In a second aspect, there is provided a backup control method forperiodic data backup in a virtualized storage system having apoint-in-time copy function operable to copy first data into a cascadeand comprising steps of: selecting, by a storage targeting component, atarget virtual disk for one of a full copy or an incremental copy of thefirst data; triggering, by a periodic backup component, a periodicpoint-in-time copy of the first data to a virtual disk in the cascade;testing, by a testing component, a status of the full copy, theincremental copy and the periodic point-in-time copy; and responsive tothe status, splitting, by a cascade splitting component, the cascade toremove a dependency relationship of at least one of the full copy, theincremental copy and the periodic point-in-time copy on the first data.

In one embodiment, the cascade splitting component is operable toselectively reattach the at least one of the full copy, the incrementalcopy and the periodic point-in-time copy at a different position in thecascade. In one embodiment, the cascade is controllable by means of arelocatable cascade disk mapping. In one embodiment, the point-in-timecopy function comprises FlashCopy. In one embodiment, the relocatablecascade disk mapping comprises a FlashCopy Fdisk. In one embodiment, theat least one of the full copy, the incremental copy and the periodicpoint-in-time copy comprises a space-efficient copy.

In a third aspect, there is provided a computer program comprisingcomputer program code to, when loaded into a computer system andexecuted thereon, cause the computer system to perform the steps of amethod according to the second aspect.

The illustrated embodiments of the present invention thus advantageouslyprovide an apparatus and method for providing storage-efficient periodicdata backups while reducing the risk of data corruption or loss.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict embodiments of the invention and are not therefore to beconsidered to be limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings, in which:

FIG. 1 a is a block diagram illustrating an apparatus in which anembodiment of the present invention may be implemented;

Fig. is a block diagram illustrating an apparatus according to oneembodiment of the present invention;

FIG. 2 is a flow diagram of exemplary replication according to oneembodiment of the present invention;

FIG. 3 is a flow diagram of exemplary replication method according toone embodiment of the present invention; and

FIGS. 4 to 8 show a simplified worked example of an arrangement ofstorage according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows an arrangement of apparatus 100 suitable for theimplementation of a data backup system according to one embodiment.Physical Storage (PS) 102 is the store of physical storage available forbacking up the production data. Space Efficient Storage (SE) 104 is thestore of space-efficient storage available for backing up the productiondata. FlashCopy Control (FCC) 106 controls the creation of the storagerequired for the backup, the creation, start and stop of the FlashCopiesrequired for the backup scheme. Backup Controller (BCtlr) 108 controlsthe sequence of events required to successfully execute the backuppolicy. Production Data (PD) 110 is the production data.

FIG. 1 b illustrates a portion of an exemplary apparatus 1000 for databackup according to an embodiment of the invention. The apparatus isoperable with a point-in-time copy function to copy production data 110into a cascade 1004, and comprises a storage targeting component 1006for selecting a target virtual disk for a full or incremental copy ofthe production data 110, and a periodic backup component 1008 fortriggering a periodic point-in-time copy of the production data 110 to avirtual disk in the cascade 1004. Apparatus 1000 also comprises atesting component 1010 for testing a status of the full copy, theincremental copy and the periodic point-in-time copy and a cascadesplitting component 1012 responsive to the status for splitting thecascade 1004 to remove a dependency relationship of at least one of thefull copy, the incremental copy and the periodic point-in-time copy onthe production data 110.

In one embodiment, the backup control apparatus 1000 is arranged suchthat the cascade splitting component 1008 is operable to selectivelyreattach the at least one of the full copy, the incremental copy and theperiodic point-in-time copy at a different position in the cascade.

In one embodiment, the backup control apparatus 1000 is arranged suchthat the full copy, the incremental copy and the periodic point-in-timecopy may comprise space-efficient copies in which, although the targetvirtual disk is defined to the system (for example, to a host computer)as being of the same size as the source, it is in fact only as large asnecessary to accommodate the actual data that has been written to thesource disk, thus saving any space that would otherwise have been takenup with copies of the unwritten portions of the source disk.

An exemplary method according to one embodiment is broadly as follows:

The user specifies the production data 110 to be protected, thefrequency of backup and the physical storage 102 to be used for backingup the data. All instructions are sent from backup controller 108 toFlashCopy control 106. Initially backup controller 108 instructsFlashCopy control 106 to create an incremental FlashCopy map ofproduction data 110 using storage from physical storage 102 for thetarget disk. From then on backup controller 108 performs the steps ofthe method as shown in FIG. 2 when the backup system is first startedand every time the period between backups expires.

The process steps or logic functions of a logic apparatus operate asshown in the flowchart of FIG. 2, in which the process begins at startstep 200. At step 202 the target space-efficient Vdisk is acquired byspace-efficient storage 104 on command from FlashCopy control 106 asinstructed by backup controller and test step 204 determines whether thefull copy is complete. If the full copy is not complete step 208 beginsthe copy of the production data Vdisk to the new target disk and teststep 210 determines whether the full copy has been started. If thedetermination at test step 210 is that the full copy has been started,the process waits for the specified period at step 214 before returningto step 202. If test step 210 determines that the full copy has not beenstarted, the incremental map is started at step 212 and the processwaits for the specified period at step 214 before returning to step 202.If test step 204 determines that the full copy is complete, step 206starts the copy of the target Vdisk of the full copy onto the new targetVdisk and then proceeds to start the incremental map at step 212. Afterstarting the incremental map, the process waits for the specified periodat step 214 before returning to step 202.

When the incremental FlashCopy completes, backup controller 108 performsthe further steps of the method as shown in FIG. 3.

The process steps or logic functions of a logic apparatus operate asshown in the flowchart of FIG. 3, in which the process begins when thefull copy completes at step 300. At step 302, the full copy is removedfrom the cascade by splitting the cascade, and test step determineswhether the full copy is the latest copy. If the full copy is determinedat test step 304 not to be the latest copy, step 308 starts theincremental map and the process exits at step 306. If the full copy isdetermined at test step 304 to be the latest copy, the process exits atstep 306.

Splitting the cascade according to one embodiment relies on a method forremoving a map from a cascade by means of Fdisks. An Fdisk, which is adata structure internal to FlashCopy, is used to represent the source ortarget disk for a given FlashCopy mapping in the cascade. The use ofFdisks enables FlashCopy mappings to be manipulated by allowing a Vdiskto be represented in multiple cascades or at multiple points in the samecascade by different Fdisks. A first Fdisk will represent the VDisk thatis being presented to the host and the other Fdisks will represent theVDisk required to maintain the cascade at other points.

The act of splitting the cascade means that, when the incremental map isretriggered, any maps downstream of the incremental map are attached tothe secondary Fdisk and any Fdisks initially downstream of the secondaryFdisk are moved to the end of the cascade. This modification is possiblein this case because any data on targets initially downstream of theprimary Fdisk cannot be needed by the targets downstream of thesecondary Fdisk.

A worked example will now be described, with reference to FIGS. 4 to 8.

Initially the arrangement of disks and contents is as shown in FIG. 4.In FIG. 4 are shown production data Vdisk 400 operatively connected forI/O redirection to production data primary Fdisk 402. Production dataprimary Fdisk 402 is operatively connected for incremental mapping tofull copy primary Fdisk 406, which in turn is operatively connected forI/O redirection to full copy Vdisk 404. Full copy primary Fdisk 406 isoperatively connected for backup to target 1 space-efficient primaryFdisk 410, which in turn is operatively connected for I/O redirection totarget space-efficient Vdisk 408.

In this arrangement the production data is protected from corruptionwith RPO the start of the backup 1. The system is not protected fromdata loss until the full copy is complete. From the above arrangement wehave two possibilities: either the period between backups expires beforethe incremental map completes or it does not. This depends on the amountof data that needs to be copied and the period used for taking thecopies. So, if the full copy completes before a new copy is taken, thearrangement of disks and contents is as shown in FIG. 5.

In FIG. 5, wherein the numbered references are as in FIG. 4, it can beseen that the incremental map relationship between production dataprimary Fdisk 402 and full copy primary Fdisk 406 has been severed.

If the period expires before the incremental map completes, thearrangement of disks and contents is as shown in FIG. 6. In FIG. 6,wherein numbered references 400-410 are as in FIG. 4, it can be seenthat the pairing of target 2 space-efficient Vdisk 600 and target 2space-efficient primary Fdisk, to which it is operatively connected forI/O redirection, has been interposed between pairing 400/402 and pairing404/406. Backup 2 relationship is now established between productiondata primary Fdisk 402 and target 2 space-efficient primary Fdisk 602,and incremental map relationship is now established between target 2space-efficient primary Fdisk 602 and full copy primary Fdisk 406.

Now when the period expires in the first arrangement or the incrementalmap completes in the second arrangement, the arrangement of disks andcontents is as shown in FIG. 7. Backup 1 continues now between the newpairing of full copy secondary Fdisk 700/full copy Vdisk 702 and theexisting pairing 408/410, isolated from the incremental map relationshipbetween pairing 400/402 and 404/406 and also from the backup 2relationship between pairing 404/406 and 600/602.

In this arrangement the production data is protected from corruption anddata loss with RPO the start of backup 1. The production data isprotected from data corruption with RPO the start of backup 2. When theincremental copy completes and the time-out has expired, the arrangementof disks and contents is as shown in FIG. 8, in which backup 1 andbackup 2 are isolated from the production data and backup 3 relationshiphas been started. In this arrangement the production data is protectedfrom corruption and data loss with RPO the start of the backup 2.

Thus it can be seen that this method allows backups (and in particular,space-efficient backups) to be collected that protect the productiondata from data loss and data corruption. These copies subsequentlymaintain this level of protection. It will be clear to one of ordinaryskill in the art that, because of the removal of dependencies asdescribed herein, the user can conveniently remove copies that are nolonger needed, and that the production data can be recovered from anybackup copy.

Embodiments of the invention thus provide an apparatus and method forproviding periodic data backups while reducing the risk of datacorruption or loss. It will be clear to one of ordinary skill in the artthat all or part of the method of one embodiment of the presentinvention may suitably and usefully be embodied in a logic apparatus, ora plurality of logic apparatus, comprising logic elements arranged toperform the steps of the method and that such logic elements maycomprise hardware components, firmware components or a combinationthereof.

It will be equally clear to one of skill in the art that all or part ofa logic arrangement according to one embodiment of the present inventionmay suitably be embodied in a logic apparatus comprising logic elementsto perform the steps of the method, and that such logic elements maycomprise components such as logic gates in, for example a programmablelogic array or application-specific integrated circuit. Such a logicarrangement may further be embodied in enabling elements for temporarilyor permanently establishing logic structures in such an array or circuitusing, for example, a virtual hardware descriptor language, which may bestored and transmitted using fixed or transmittable carrier media.

It will be appreciated that the method and arrangement described abovemay also suitably be carried out fully or partially in software runningon one or more processors (not shown in the figures), and that thesoftware may be provided in the form of one or more computer programelements carried on any suitable data-carrier (also not shown in thefigures) such as a magnetic or optical disk or the like. Channels forthe transmission of data may likewise comprise storage media of alldescriptions as well as signal-carrying media, such as wired or wirelesssignal-carrying media.

A method is generally conceived to be a self-consistent sequence ofsteps leading to a desired result. These steps require physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated. It is convenient at times, principally for reasons ofcommon usage, to refer to these signals as bits, values, parameters,items, elements, objects, symbols, characters, terms, numbers, or thelike. It should be noted, however, that all of these terms and similarterms are to be associated with the appropriate physical quantities andare merely convenient labels applied to these quantities.

The present invention may further suitably be embodied as a computerprogram product for use with a computer system. Such an implementationmay comprise a series of computer-readable instructions either fixed ona tangible medium, such as a computer readable medium, for example,diskette, CD-ROM, ROM, or hard disk, or transmittable to a computersystem, via a modem or other interface device, over either a tangiblemedium, including but not limited to optical or analogue communicationslines, or intangibly using wireless techniques, including but notlimited to microwave, infrared or other transmission techniques. Theseries of computer readable instructions embodies all or part of thefunctionality previously described herein.

Those skilled in the art will appreciate that such computer readableinstructions can be written in a number of programming languages for usewith many computer architectures or operating systems. Further, suchinstructions may be stored using any memory technology, present orfuture, including but not limited to, semiconductor, magnetic, oroptical, or transmitted using any communications technology, present orfuture, including but not limited to optical, infrared, or microwave. Itis contemplated that such a computer program product may be distributedas a removable medium with accompanying printed or electronicdocumentation, for example, shrink-wrapped software, pre-loaded with acomputer system, for example, on a system ROM or fixed disk, ordistributed from a server or electronic bulletin board over a network,for example, the Internet or World Wide Web.

In one alternative, one embodiment of the present invention may berealized in the form of a computer implemented method of deploying aservice comprising steps of deploying computer program code operable tocause the computer system to perform all the steps of the method whendeployed into a computer infrastructure and executed thereon.

In a further alternative, one embodiment of the present invention may berealized in the form of a data carrier having functional data thereon,the functional data comprising functional computer data structures to,when loaded into a computer system and operated upon thereby, enable thecomputer system to perform all the steps of the method.

The flowchart and block diagram in the above figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While one or more embodiments of the present invention have beenillustrated in detail, one of ordinary skill in the art will appreciatethat modifications and adaptations to those embodiments may be madewithout departing from the scope of the present invention as set forthin the following claims.

1. A backup control apparatus for periodic data backup in a virtualizedstorage system having a point-in-time copy function operable to copyfirst data into a cascade and comprising: a storage targeting componentfor selecting a target virtual disk for one of a full copy or anincremental copy of the first data; a periodic backup component fortriggering a periodic point-in-time copy of the first data to a virtualdisk in the cascade; a testing component for testing a status of thefull copy, the incremental copy and the periodic point-in-time copy; anda cascade splitting component responsive to the status for splitting thecascade to remove a dependency relationship of at least one of the fullcopy, the incremental copy and the periodic point-in-time copy on thefirst data.
 2. The backup control apparatus of claim 1, wherein thecascade splitting component is operable to selectively reattach the atleast one of the full copy, the incremental copy and the periodicpoint-in-time copy at a different position in the cascade.
 3. The backupcontrol apparatus of claim 1, wherein the cascade is controllable bymeans of a relocatable cascade disk mapping.
 4. The backup controlapparatus of claim 1, wherein the point-in-time copy function comprisesFlashCopy.
 5. The backup control apparatus of claim 4, wherein therelocatable cascade disk mapping comprises a FlashCopy Fdisk.
 6. Thebackup control apparatus of claim 1, wherein the at least one of thefull copy, the incremental copy and the periodic point-in-time copycomprises a space-efficient copy.
 7. A method for ensuring periodic databackup control in a virtualized storage system having a point-in-timecopy function operable to copy first data into a cascade and comprisingsteps of: selecting, by a storage targeting component, a target virtualdisk for one of a full copy or an incremental copy of the first data;triggering, by a periodic backup component, a periodic point-in-timecopy of the first data to a virtual disk in the cascade; testing, by atesting component, a status of the full copy, the incremental copy andthe periodic point-in-time copy; and responsive to the status,splitting, by a cascade splitting component, the cascade to remove adependency relationship of at least one of the full copy, theincremental copy and the periodic point-in-time copy on the first data.8. The backup control method of claim 7, further including selectivelyreattaching, by the cascade splitting component, the at least one of thefull copy, the incremental copy and the periodic point-in-time copy at adifferent position in the cascade.
 9. The backup control method of claim7, wherein the cascade is controllable by means of a relocatable cascadedisk mapping.
 10. The backup control method of claim 7, wherein thepoint-in-time copy function comprises FlashCopy.
 11. The backup controlmethod of claim 9, wherein the relocatable cascade disk mappingcomprises a FlashCopy Fdisk.
 12. The backup control method of claim 7,wherein the at least one of the full copy, the incremental copy and theperiodic point-in-time copy comprises a space-efficient copy.
 13. Acomputer program product for ensuring periodic data backup control in avirtualized storage system having a point-in-time copy function operableto copy first data into a cascade and comprising in a computing storageenvironment by a processor device, each of the storage resources havinga resource policy object including a resource group attributeassociating the resource policy object with at least one of theplurality of resource groups, the computer program product comprising acomputer-readable storage medium having computer-readable program codeportions stored therein, the computer-readable program code portionscomprising: a first executable portion for selecting, by a storagetargeting component, a target virtual disk for one of a full copy or anincremental copy of the first data; a second executable portion fortriggering, by a periodic backup component, a periodic point-in-timecopy of the first data to a virtual disk in the cascade; a thirdexecutable portion for testing, by a testing component, a status of thefull copy, the incremental copy and the periodic point-in-time copy; anda fourth executable portion for responsive to the status, splitting, bya cascade splitting component, the cascade to remove a dependencyrelationship of at least one of the full copy, the incremental copy andthe periodic point-in-time copy on the first data.
 14. The computerprogram product of claim 13, further including a fifth executableportion for selectively reattaching, by the cascade splitting component,the at least one of the full copy, the incremental copy and the periodicpoint-in-time copy at a different position in the cascade.
 15. Thecomputer program product of claim 13, further including a fifthexecutable portion for controlling the cascade via a relocatable cascadedisk mapping.
 16. The computer program product of claim 13, furtherincluding a fifth executable portion for performing a FlashCopy in thepoint-in-time copy function.
 17. The computer program product of claim15, further including a sixth executable portion for initializing aFlashCopy Fdisk in the relocatable cascade disk mapping.
 18. Thecomputer program product of claim 13, further including a fifthexecutable portion for performing a space-efficient copy in the at leastone of the full copy, the incremental copy and the periodicpoint-in-time copy.